Many forms of cut-pile knitted fabric are known and produced in the textile industry. One of the most popular forms of this type of fabric is knitted velour, a plush knit construction produced by knitting two yarns in plating relationship, one yarn forming pile loops which appear on the plush surface of the fabric and the other yarn forming the base or body of the fabric. In other conventional forms of cut-pile fabric, the pile yarn, rather than actually being knitted with the base or body yarn, is inlaid or otherwise incorporated unknit in the base of body fabric. Cut-pile fabrics of these types are conventionally produced on circular knitting machines utilizing a cylinder of knitting needles in conjunction with specially constructed pile loop forming sinkers. Thus, for example, velour has traditionally been produced on circular knitting machines using specially constructed sinkers capable of forming loops on two levels. Two yarns are fed to the knitting needles, the yarn which is to form the plush or pile loops being fed over the top loop forming level of the sinker and the base yarn being fed over the lower loop forming level. In this manner, loops of two different heights are created, the shorter loops forming the base and appearing on the plain side of the finished fabric and the longer loops forming the surface or pile loops which appear on the purl side of the finished fabric. The above-mentioned pile fabric having an inlaid pile yarn is similarly produced, except that the pile yarn is fed and manipulated in such a manner that it is incorporated unknit in the stitches of the body fabric.
As will be understood, the knitted fabrics produced by the above-described methods contain uncut pile loops, which must be further processed after knitting is completed to produce cut-pile ends by shearing of the longer surface pile loops, i.e. cutting off the top portion of each pile loop thereby leaving two cut-pile ends extending outwardly from the fabric surface and being anchored in the base by virtue of having been knit in plating relationship with the base yarn, inlaid in the body fabric or otherwise incorporated therein. Brushing or napping of the fabric may be performed either for the purpose of breaking the surface loops, thus serving as a substitute for shearing, or as an additional step subsequent to shearing to raise the individual fibers in the cut ends to enhance the plush surface effect and feel of velour. Tigering may also be desirable to remove surplus fiber strands from the napped fabric surface.
Although the foregoing known methods produce desirable results, there are significant disadvantages. Substantial labor and production costs are inherently involved in performing the finishing steps of shearing, brushing and tigering and there is a significant fiber waste resulting from the shearing and napping procedures. In fact, in conventional velour production as much as 20-25% of the pile yarn knitted is sheared and thrown away. The percentage is significantly higher in the production of other forms of cut-pile fabric in which the pile yarn is inlaid or otherwise incorporated in the base fabric unknit since the pile loops comprise most of the pile yarn employed in such knitting. Compounding this problem is the fact that the shearing process involves the risk of failing to shear some of the plush loops, especially when one is attempting to reduce the amount of fiber waste by shearing at a reduced nap depth. Because of this, it is often necessary to perform the shearing step twice to achieve first quality cut-pile fabric. Alternatively, the danger of damaging the fabric exists when shearing is performed at a greater nap depth or more than once in an attempt to insure the shearing of all pile loops. A still further disadvantage is that, because of the necessary shearing step in producing velour, polyester velour generally cannot feasibly be produced due to the excessive dulling effect that polyester yarn has on the shearing blades of the typical shearing machine. Finally, in conventional cut-pile fabric knitting, great attention must be paid to the nature of the pile loops formed and to the type of yarn used to form the pile loops since the torque of the pile yarn can cause significant problems in shearing the pile loops. If the torque or twist of the pile yarn is too great, the pile loops will tend to spiral after leaving the loop forming sinkers. This spiraling effect makes shearing of the pile loops more difficult in that the loops themselves become harder to shear and in that the loops are less prone to extend outwardly from the fabric surface thereby increasing the likely number of unsheared loops.
In contrast, the present invention provides a novel method and apparatus for producing cut-pile fabric in which the pile loops of the fabric are cut at the top of each loop during the knitting cycle. The shearing step may be entirely eliminated, while at the same time virtually no fiber waste is involved thereby greatly reducing production costs. While shearing of the cut-pile fabric produced by the present invention may sometimes be desirable as a cleaning step, only one shearing would be necessary and only approximately 5% of the pile yarn would be cut and thrown away. As a result, a more expensive pile yarn may be utilized in the present invention without increasing the cost of fabric production. Additionally, under the present invention every loop is cut, thereby substantially eliminating unsheared loops as a cause of defective cloth. Since the pile loops are cut at the crest of each loop, the size of the pile loop which must be formed to achieve the same pile height as produced on conventional machines is also decreased, thereby allowing still further reductions in the amount of yarn used. On the other hand, because less loop yarn is cut away in the finishing procedures by using the invention herein described, the resultant cut ends may be made significantly higher if desired without increasing production costs. Additionally, fabric producers are no longer limited to utilizing cotton yarns since, according to the present invention, the dulling effect involved in the cutting of synthetic fibers is greatly reduced. Finally, since the pile loops are cut during the knitting operation and before any twisting or spiraling of the loops occurs, the torque of the pile yarn becomes immaterial, thus a wider range of yarn types may be used in employing the present invention.
By virtue of performing the cutting operation during the knitting operation, it also becomes feasible to produce knitted cut-pile fabric in patterns other than the plain jersey pattern conventionally used. For conventional cut-pile fabric production, in order to properly shear the pile loops of the knitted fabric, it is necessary that the loops extend substantially perpendicularly from the fabric surface to facilitate uniform shearing and, therefore, a high density of pile loops in the knitted fabric is desirable, if not necessary, for successful shearing, the high density of loops giving greater lateral support to the pile loops. Because of this, a single or plain jersey stitch pattern is used almost exclusively in conventional cut-pile fabric production in order to achieve maximum pile loop density. In contrast, since, according to the present invention, pile loops are cut during the knitting operation, the density of the pile of the knitted fabric is not a limiting factor. Thus, a much wider variety of stitch patterning becomes available to the knit fabric producer in employing the present invention. It therefore becomes possible to produce cut-pile fabrics using stitch patterns employing significantly fewer needles per inch than plain jersey or stitch patterns in which only selected needles participate in the knitting of any one course. As a result, much weaker yarns or yarns with a softer twist may be used to form the pile loops since a lesser number of needles will be acting on the pile yarn at any one time. On the other hand, considerably higher pile loops may be formed than is possible using a plain jersey stitch pattern since the number of needles putting tension on the pile loops will be reduced. A softer plusher fabric is therefore possible. Additionally, by employing heretofore unconventional stitch patterns in producing cut-pile fabric, surface color effects (e.g. a tweed effect) may be achieved merely by employing different color pile yarns. In contrast, only coursewise stripe effects may be produced in using different color yarns in a jersey pattern.